Re: [Qemu-devel] [PATCH v2 2/3] net/filter.c: Add Options to insert filters anywhere in the filter list

["Zhang, Chen" <chen.zhang@intel.com>]

> -----Original Message-----
> From: Lukas Straub <lukasstraub2@web.de>
> Sent: Friday, August 23, 2019 2:21 PM
> To: Zhang, Chen <chen.zhang@intel.com>
> Cc: qemu-devel <qemu-devel@nongnu.org>; Jason Wang
> <jasowang@redhat.com>; Wen Congyang <wencongyang2@huawei.com>;
> Xie Changlong <xiechanglong.d@gmail.com>
> Subject: Re: [PATCH v2 2/3] net/filter.c: Add Options to insert filters
> anywhere in the filter list
> 
> On Fri, 23 Aug 2019 03:24:02 +0000
> "Zhang, Chen" <chen.zhang@intel.com> wrote:
> 
> > > -----Original Message-----
> > > From: Lukas Straub [mailto:lukasstraub2@web.de]
> > > Sent: Friday, August 16, 2019 2:49 AM
> > > To: qemu-devel <qemu-devel@nongnu.org>
> > > Cc: Zhang, Chen <chen.zhang@intel.com>; Jason Wang
> > > <jasowang@redhat.com>; Wen Congyang
> <wencongyang2@huawei.com>; Xie
> > > Changlong <xiechanglong.d@gmail.com>
> > > Subject: [PATCH v2 2/3] net/filter.c: Add Options to insert filters
> > > anywhere in the filter list
> > >
> > > To switch the Secondary to Primary, we need to insert new filters
> > > before the filter-rewriter.
> > >
> > > Add the options insert= and position= to be able to insert filters
> > > anywhere in the filter list.
> > >
> > > position should be either "head", "tail" or the id of another filter.
> > > insert should be either "before" or "after" to specify where to
> > > insert the new filter relative to the one specified with position.
> > >
> >
> > Hi Lukas,
> >
> > It looks no need to add the "insert = xxx" for this operation.
> > For example:
> >
> > We have 3 net-filters, the running order like that:
> >
> > Fiter1   ---------->   Filter2 ------------> Filter3
> >
> > If we want to add another filter between filter1 and filter2.
> > The "Position = head, insert = after" always seam with "position = filter2 id,
> insert = before".
> 
> Hi Zhang,
> The insert= parameter is ignored if position=head or tail. It always Inserts at
> the head (before Filter1) or the tail (after Filter3) of the List in these cases.
> 
> > It seems the "insert" is a redundant args.
> > So I think it is enough with the "position", we can make the "insert" always
> equal "after" except the "head".
> 
> Yes, we still could do it without it, but its more convenient with the insert=
> parameter. For example our Case with inserting before the rewriter:
> 
> 'filter-mirror', 'id': 'm0', 'props': { 'insert': 'before', 'position': 'rew0', 'netdev':
> 'hn0', 'queue': 'tx', 'outdev': 'mirror0' } 'filter-redirector', 'id': 'redire0', 'props':
> { 'insert': 'before', 'position': 'rew0', 'netdev': 'hn0', 'queue': 'rx', 'indev':
> 'compare_out' } 'filter-redirector', 'id': 'redire1', 'props': { 'insert': 'before',
> 'position': 'rew0', 'netdev': 'hn0', 'queue': 'rx', 'outdev': 'compare0' }
> 
> You see directly that here 3 Filters are inserted before the rewriter.
> 
> would have to become:
> 
> 'filter-mirror', 'id': 'm0', 'props': { 'position': 'head', 'netdev': 'hn0', 'queue': 'tx',
> 'outdev': 'mirror0' } 'filter-redirector', 'id': 'redire0', 'props': { 'position': 'm0',
> 'netdev': 'hn0', 'queue': 'rx', 'indev': 'compare_out' } 'filter-redirector', 'id':
> 'redire1', 'props': { 'position': 'redire0', 'netdev': 'hn0', 'queue': 'rx', 'outdev':
> 'compare0' }
> 
> Which is less obvious.

OK, It is fine for me.
But in the code have some other issues like that:

+
+static void netfilter_set_insert(Object *obj, const char *str, Error **errp)
+{
+    NetFilterState *nf = NETFILTER(obj);
+
+    if (strcmp(str, "before") && strcmp(str, "after")) {                                
+        error_setg(errp, "Invalid value for netfilter insert, " 
+                         "should be 'head' or 'tail'");                                  -------------------------------->>> I think you should change the "head/tail"  to "before/after".
+        return;
+    }
+
+    nf->insert_before = !strcmp(str, "before");
+}


And I think the "front/behind" is better than "before/after" in this status.
At the same time the name of the "insert_before" change to "front_flag" is better.


Thanks
Zhang Chen

> 
> Regards,
> Lukas Straub
> 
> >
> > Thanks
> > Zhang Chen
> >
> > > Signed-off-by: Lukas Straub <lukasstraub2@web.de>
> > > ---
> > >  include/net/filter.h |  2 ++
> > >  net/filter.c         | 71
> +++++++++++++++++++++++++++++++++++++++++++-
> > >  qemu-options.hx      | 10 +++----
> > >  3 files changed, 77 insertions(+), 6 deletions(-)